Creep Analysis in Abaqus

[Rohan Ahrawal]

I'm performing a creep analysis on a dogbone specimen made of SS-304. I am following this paper Correlation Analysis of Established Creep Failure Models through Computational Modelling for SS-304 Material.

Following is the geometry:

In property module I've created the material, specifying Young's modulus (201000 MPa) and Poisson's ratio (0.31) on sheet "Elastic" and specifying Power Law Multiplier (6.18e-17), equation stress order (6.82) and time order (0) in sheet "Creep".

Then I create Visco step in Step module, specifying a time period of 6480000 sec (18000 Hr); in the sheet "Incrementation" I've chosen the max number of increment (10000), Initial increment size (1), minimum (1e-20) and max (360000), then I've chosen creep/swlling...tolerance (0.1).

After that I've created a coupling constraint in Interaction module, then a reference point for the whole grip section with neck section of the specimen.



I've created a symmetry BC for the bottom section of grip and neck.



Then I've defined a load (displacement) of 2mm Magnitude. Also a thermal field is also defined of 720°C.



I've done the mesh, I’ve created and started the job, but I am getting wrong stress results but the creep results are somewhat In line. More over the creep curve trend also matched that of the literature, But not for stress results,



Any suggestion on how to fix the problem.

 

[FEA way]

One image is missing. It's much better to upload images directly here instead of using 3rd party hosting services where files may disappear after some time.

So you took one material model case from the article. BCs seem to be applied differently in your model. Exactly which figures from the article are you using for comparison ? Is Figure 6 one of them ?

 

[Rohan Ahrawal]

One image is missing. It's much better to upload images directly here instead of using 3rd party hosting services where files may disappear after some time.

So you took one material model case from the article. BCs seem to be applied differently in your model. Exactly which figures from the article are you using for comparison ? Is Figure 6 one of them ?

While modelling I also thought that I might be using wrong BCs. In the paper it is written "One end of the specimen was fixed, and the displacement was set at the other end with an amplitude of 2 mm/min". I am not quite understanding it. And for material properties I have only specified elastic and creep properties for SS-304 do I need to specify density, thermal expansion and other properties?

 

[FEA way]

In the paper it is written "One end of the specimen was fixed, and the displacement was set at the other end with an amplitude of 2 mm/min". I am not quite understanding it.

Yes, this paper is quite unclear, especially when it comes to the description of the setup. That’s unfortunately quite common in scientific articles.

They mention velocity here but then write about steady (force?) load which makes sense for creep analysis.

It might be difficult to properly recreate the results from this paper with such unclear and limited descriptions.

And for material properties I have only specified elastic and creep properties for SS-304 do I need to specify density, thermal expansion and other properties?

You need density only for inertia effects and thermal expansion only if you want to take this effect occuring due to temperature change into account.